Every Forbidden Food Has Its Permitted Counterpart in Torah

[These are the creatures that you may eat (Leviticus 11:2).] The Holy One, blessed be He, said [to him]: Warn Israel not to eat bad things, so that your evil inclination should not lead you astray, saying that the Holy One has forbidden good things to Israel. The Holy One said: Everything that I have forbidden to you, I have permitted to you something corresponding to it. I forbade to you the blood of a menstruant; I permitted to you the blood of virginity. [I forbade to you the blood; I permitted to you the spleen and the liver, which are entirely blood.] I forbade to you the flesh of swine; I permitted to you the tongue of a fish whose name is shibbuta, which resembles swine. I forbade to you a married woman; I permitted to you the woman of beautiful form, [as it is said, And you see among the captives a woman of beautiful form, and you desire her, and would take her to yourself for a wife (Deuteronomy 21:11).] I forbade to you a brother's wife; I permitted her to you after his death, [as it is said,] Her brother-in-law shall come in unto her [and take her to himself for a wife] (Deuteronomy 25:5). I forbade to you mingled kinds (kilayim), but I permitted to you a linen sheet with woolen fringes. I forbade to you the fat of a domestic animal, but I permitted to you that of a wild animal. Rabbi Bisna said in the name of Rabbi Hiyya: What the Holy One forbade in a domestic animal He permitted in a wild animal, and what He forbade in fowl He permitted in fish. How so? He forbade fat in a domestic animal; He permitted it in a wild animal. He forbade the sinew of the thigh-vein in a wild animal; He permitted it in fowl. He forbade blood in fowl; He permitted it in fish. And why all this? In order to give a good reward to Israel for observing the commandments.